River sediments

Benefits

RapidEye images can assess moderate suspended sediment concentrations of intermittent rivers (67-223 mg/L), even when their discharge is low. The RapidEye indices performed better than those from literature.

Limitations

Hydrological characteristics of semi-arid intermittent rivers generate difficulties to monitor suspended sediment concentrations using optical satellite remote sensing, such as time-concentrated sediment yield; and its association with recent rainfall events and, therefore, with cloudy sky.

Applicability for Northland

Yes, likely.

An important limitation would come from the need to acquire high-resolution imagery, which at the moment is not available freely, and would therefore induce monitoring costs.

Techniques applying optical data will be limited in coverage and temporal granularity by the persistent cloud cover in the region, particularly during the winter months. Mature cloud-masking techniques are directly available for open access multispectral data (e.g. Landsat and Sentinel-2). When using commercial data, care must be taken to ensure that there is sufficiently cloud free imagery available, as cloud masking is not as mature and ordering a large volume of imagery to ensure complete cloud free coverage between multiple observations can become cost prohibitive.